The present invention relates to a resin composition containing polyphenylene ether resin which can be made into shaped articles, sheets and the like by injection molding, extrusion molding, blow molding, and the like.
More particularly, it relates to a thermoplastic resin composition which comprises a resin composition comprising a polyphenylene ether and a thermoplastic polyester, to which is added an aliphatic hydroxycarboxylic acid or a derivative thereof. This thermoplastic resin composition has excellent mechanical properties, processability, solvent resistance and chemical resistance.
Polyphenylene ether resin has excellent heat resistance, but has difficulties in processability and solvent resistance, whereby the scope of use thereof is limited.
In order to improve processability and impact strength, blends of polyphenylene ether with styrene resin have been widely used. However, these resin compositions still have problems in solvent resistance and scope of their use is also limited. For example, they are not suitable to the field which requires endurance against solvents such as gasoline.
On the other hand, thermoplastic polyesters represented by polybutylene terephthalate and polyethylene terephthalate are superior in solvent resistance and are widely used for automobile parts, electric and electronic parts and other mechanical parts.
However, these polyesters have defects such as low heat distortion temperature, large molding shrinkage, great linear expansion coefficient and hence they cannot be applied, as they are, to the uses where load is applied at high temperatures or dimensional accuracy is required. Therefore, it has been proposed to incorporate therein reinforcing agents such as glass fibers, but the molded articles have defects such as poor appearance and warpage. Therefore, these resins cannot be applied to the uses which require severe conditions for appearance and shapes such as outer ply materials of automobiles.
A composition of polyphenylene ether and polyester as one which offsets the defects and makes use of the best characteristics of both resins has been proposed, for example, in Japanese Patent Kokoku No. 51-21664.
In the coposition proposed, compatibility between polyphenylene ether resin and polyester resin is very poor which results in insufficient mechanical properties and oil resistance. Besides, molded articles obtained by injection molding or the like are inferior in surface appearance due to insufficient dispersion of polyphenylene ether and polyester.
Therefore, use of a so-called compatibilizing agent has been proposed in order to improve dispersibility of the polyphenylene ether phase, the polyester phase and stabilize the phase.
For example, Japanese Patent Kokai No. 60-221459 has proposed addition of a styrene resin having an epoxy group and Japanese Patent Kokai Nos. 62-257958 and 63-350 have proposed adding a compatibilizing agent such as maleic anhydride having simultaneously an unsaturated group and a carboxyl group or derivative thereof.